Marking playing fields



Unite States Patent Filed Nov. 4, 1957, Ser. No. 694,084 1 Claim. (CI. 94-22) No Drawing.

This invention relates to marking playing fields and particularly to holding on the soil a low density powder that normally is subject to being blown away by wind.

In marking lines on football, baseball, tennis and other playing fields, it is customary to use lime or a ground stone. The lime is caustic. It is irritating or injurious to the eyes and skin. The ground stone, on the other hand, has a tendency to pack to a hard abrading surface that is also undesirable to those who fall upon it.

Diatomaceous earth in powder form is known to be free from these objections and also to be extremely bulky and light, so that only a small weight is required for a band of given area and thickness. Diatomaceous earth has not been used, however, for marking playing fields in advance of the present discovery for the reason that the extremely light, flufiy, easily wind-blown powder is subject to distortion of the applied lines in a draft of air or actual removal by wind.

I have now discovered a simple and effective means of holding the diatomaceous earth at the selected position of marking lines on a dirt sports field so that the applied diatomaceous earth is satisfactorily resistant to distortion and to being blown away.

Briefly stated, the invention comprises applying finely divided diatomaceous earth in combination with water,

applied in a slurry or separately by dew or rain, so that the water filters into the surface portion of the dirt or grass of the playing field, carries a part of the diatomaceous earth into intimate contact with the soil, and deposits this part in the pores in the soil so that capillarity is established between the soil and the overlying layer or strip of diatomaceous earth. This capillarity so established continues and keeps the diatomaceous earth, always very absorptive of water, slightly moist during seasons of reasonable soil moisture. In moist condition, the diatomaceous earth does not blow objectionably in any ordinary wind.

The diatomaceous earth used is finely divided so that it will pass substantially completely through a SO-rnesh screen or to the extent of at least 95% 'by weight through 60 mesh. It is amorphous and used at a pH of 6-10.

The marking material described lasts longer on the playing field as the material is insoluble in water and chemically inert. It neither disappears by solution and complete penetration into the ground nor cakes into stony or hard condition. It feeds easily from a usual lime spreader. It retains its reflective power, particularly when in the flux calcined (white) form, even when wet and under either day or night lighting.

For proper anchoring into the soil, so as to avoid blowing away of what would be expected to be a very unsatisfactory material for the purpose, the marking material is applied ordinarily in slurry form. Dry application may be made only when atmospheric or surface conditions will ensure wetting of the material within reasonable time, as by dew or rain. Once the material is wet and capillary contact with the ground is established, additional wetting is not required.

The diatomaceous earth may and suitably does contain a small amount of a potential binder that, when moistened and then dried, provides some slight bond between the siliceous particles constituting the major part of the diatomaceous earth. Thus I may use a diatomaceous earth containing clay, as in the proportion of 1-20 parts for 100 of the diatomaceous earth. The clay used may be that present in the particular grade of diatomaceons earth chosen for use or may be admixed clay, in which case it should be at least reasonably bright in color when viewed under light. In place of the clay as binder I may use an equal amount of talc or a small amount of alkali metal silicate. The silicate may be in the proportion of about 0.2%-5% of the diatomaceous earth and fused into it so as to be largely insolube in nvater. The silicate may be a part of the diatomaceous earth that has been calcined in powder form at about 1000" C., as with an alkali metal flux such as sodium or potassium chloride, carbonate or silicate and then disintegrated by light milling again to powder of the fineness stated.

Pigments to increase the brightness may be introduced as, (for instance, 1% or so of titanium dioxide, zinc om'de, V

whiting or like pigments, the proportion being increased with such relatively less effective pigments as the whiting.

In use of the diatomaceous earth as playfield marking material, it is necessary that the material be mixed into a filterable aqueous slurry so as to penetrate, during filtering of the water into the soil, in part into the pores near the surface of the soil of the field to be marked. Examples of suitable proportions in the slurry are 1 part of the'diatomaceous earth on the dry basis for 5-20 parts of water. The slurry is made by mixing the materials in any conventional type of equipment, either hand operated or power driven. Any additives to be used are admixed into the diatomaceous earth in either powder or slurry form. The slurry is filled into a marking device and kept in agitation by rotation or otherwise to prevent settling. II use to advantage for this application, the usual type of lime markers in which a container, with a perforated circumferential band periphery or edge, rolls, on the edge, along the ground to be marked. The slurry runs through the perforations in the band periphery of the marker. The water of the slurry then filters in large proportion into the ground and causes such penetration and subsequent deposition of a minor proportion of the diatomaceous earth in surface pores of the soil as to establish capillarity with the major part of the diatomaceous earth which remains as the desired visible and now wind resistant marking band. As a result of all the effects obtained, the diatomaceous earth, which normally is easily blown away, remains in position in the strips Where the marking is desired.

When clay, sodium silicate or other potential binder material is present, the water of the slurry activates and the subsequent removal of the water firms the binder, so that the finished, dried strip of marking material has some bonding and staying property in addition to that developed by the manner of application of the filterable slurry.

The marking strip may be applied to any desired thickness, as, for example, 0.01-0.05 inch or more. The amount applied must be sufficient to establish the visible marking line.

The invention will be further illustrated by more detailed description in connection with the following specific examples. In these examples and elsewhere herein, proportions are expressed as parts by weight and all equiprnent referred to is conventional.

Example 1 Diatomaceous earth from the Quincy, Washington deposit now in commercial operation and of fineness to pass to the extent of at least through 325 mesh was mixed with water in the proportion of 1 part of the diatomaceons earth to 7 of water.

The resulting slurry was flowable, thin, and filterable. It Was transferred to the container of a manually operated lime marker which was then run over the ground in usual manner, to provide a marked strip at the desired positions on a football field covered with short grass. The material was applied in amount to leave a finished dried layer of the diatomaceous earth of average aboveground thickness about inch.

Example 2 The process and composition of Example 1 was followed except that the diatomaceous earth used was one containing approximately 6% of clay.

Example 3 The procedure of Example 1 was followed except that the diatomaceous earth used Was the high-speed filtration quality material made by calcining dia'tomaceous earth in powder form with about 5% of its weight of soda ash at approximately 1000" C. and then passing the product, after cooling, through a distintegrator to reduce the product to a powder of which more than 95% is finer than 60 mesh.

Example 4 The procedure of Example 1 is followed except that the diatomaceous earth used was mixed with of its weight ofpowdered talc before the powder was slwrried with the water.

The composition and process used give satisfactory markings when applied to playing fields. For proper visibility, it is desirable that the marking material used, namely, the diatomaceous earth or its composition with added binder, pigment or the like, should have a brightness of 65 or better on the Photovolt brightness tester, higher brightness figures being actually preferred as, for instance, 80 or so but not being necessary for adequate conspicuousness o fthe finished dried marking material.

It is to be understood that it is intended to cover all changes and modifications of the examples of the invention herein chosen for the purpose of illustration which do not constitutedepartures from the spirit and scope of the invention.

I claim:

A process of marking lines on the ground of playing fields so as to divide the area of the field into predetermined sectors which comprises applying to the surface soil of the field a sufficient amount of diatomaceous earth particles to establish a visible marking line along the boundaries of the predetermined sectors and bonding the diatom-aceous earth to the field-surface soil with the aidof Water, a supplemental water-activatable binder for the diatomaceous earth particles selected from the group consisting of clay, talc and an alkali metal silicate being included in minor proportions with the diatomaceous earth.

References Cited in the file of this patent UNITED STATES PATENTS 828,643 Dolbear Aug. 14, 1906 21,247,595 Tompkins Nov. 20, 1917 1,699,660 Forrest Jan. 22, 1929 1,764,544 Baurngardner June 17, 1930 2,013,558 Floan Sept. 3, 1935 2,235,507 Strauch Mar. 18, 1941 2,739,036 Karnenjar et a1. Mar. 20, 1956 2,824,502 Rockwell Feb. '25, 1958 2,974,030 Geary Mar. 7, 196 1 FOREIGN PATENTS 18,734 Great Britain 1909 361,653 Great Britain 1931 402,042 Great Britain 1932 OTHER REFERENCES 

